1. Field of the Invention
The present invention relates generally to the processing of seed cotton and relates more particularly to a method for delinting cotton seed.
2. Description of the Prior Art
Cotton seed, following separation from the long cotton fibers in the ginning process, is covered with short lint, also known as linters. This short lint, hereinafter referred to simply as lint, is desirably removed from the seed to facilitate the further use of the seed for planting, or the production of cotton seed oil, and to permit collection of the lint for various commercial uses.
For removing lint from seed destined for oil production, it has been conventional practice to utilize several stages of saw type delinters which comprise closely spaced rotating saw blades with fine teeth which project through a comb-like series of ribs disposed between the blades and having a narrow clearance from the blades. The lint is removed by the blade teeth and swept through the slots between the ribs while the seed is diverted by the ribs. By appropriate adjustment of the saw type delinter, most of the lint can be mechanically removed from seed destined for oil production. Such delinted seed cannot, however, be used for planting purposes since the seed is damaged to some degree by repeated contact with the saw blades during this process such that its germinating potential is significantly reduced.
Accordingly, planting seed is conventionally delinted in different types of processes, most of which use one or another form of acid treatment to clean the lint from the seed. In one such process presently in use, the lint covered seed is first subject to a flame treatment in which some of the lint is removed by burning, following which the seed is subjected to an acid treatment at elevated temperature including tumbling in rotating cylinders to disengage and chemically remove the more tenacious lint fibers from the seed.
Although acid treatment produces a relatively good end product in terms of seed germination percentage, the process itself is expensive, difficult to control, can create environmental hazards and greatly limits the effective uses of the removed lint. The lint which is not consumed by flame or acid is not suitable for a wide range of uses and frequently must be disposed of, for example by burning, and this can create additional environmental problems if prescribed safeguards are not observed. While certain key parts of the processing equipment used in the acid treatment can be fabricated from stainless steel, much of the auxiliary equipment including conveyors, tumbling cylinders, and related accessory equipment is subject to rapid corrosion and may require replacement after only a year or two of service.
From an environmental standpoint, the proposed new totally mechanical delinting system proposed herein offers an alternative which eliminates the use of chemicals and acid that can cause pollution and contamination if special equipment and precautions are not used or followed. For these reasons the mechanical delinting system and method of this application are more environmentally friendly and less likely to be adversely affected by new laws and regulations dealing with the environment.
In order to avoid the problems of acid delinting processes, it has recently been proposed to delint cotton seed by a brushing process wherein the seed passes through a stationary horizontal foraminous cylinder while subjected to the brushing action of a series of rotating brushes within the cylinder which move the seed over the screen-like apertures in the cylinders. The lint passes through the cylinder apertures and is drawn from the apparatus by an air stream while the seed passes from one end of the cylinder to the other. Several cylinders can be employed in a given machine to sequentially receive and process the seed. Such a process and equipment are shown in U.S. Pat. No. 4,942,643, issued Jul. 24, 1990.
Although the brush delinting development would if successful eliminate the acid treatment and its attendant problems, the brush type equipment has not proven capable of removing an adequate amount of lint from the cotton seed. Furthermore, the brushing of the seed produces a fairly rapid heat build-up which seems to damage the seed, reducing its germination percentage. Applicant has been unable, using a recently developed experimental brush delinter alone, to achieve germination rates higher than about 60%- 70%, which is far below a satisfactory rate. It is believed that this level of performance of the brush delinting process is typical of that which is attainable with that process.